Aseptic packages refer to sealed containers containing a substantially uniform predetermined amount of a product made in accordance with commercial aseptic packaging standards. Commercial aseptic packaging involves introducing a sterile product into a sterile container and then hermetically sealing the container in an environment substantially free of microorganisms capable of growing in a shelf stable product at temperatures at which the cooled finished product is likely to be stored during distribution and storage prior to consumption. Hermetically sealed containers minimize the transmission of any gas or fluid through the container package so that there is substantially no biological transmission. Preferably the package is also substantially free of air which, if present in significant amounts, could promote undesired microbial growth or, even in the absence of microbial growth, adversely affect the taste or color of a product. Typical products are fluent materials, specifically, a fluid drink such as milk, fruit juices, and the like.
The sterile containers commonly comprise a laminated web packaging material preferably having at least one layer of current carrying material such as aluminum foil, an exterior layer of thermoplastic material to become the package interior in contact with the product, and an exterior layer of material for contact with the environment. The laminated material, also referred to herein as "polyfoil web", is typically strong enough to stand upright in a somewhat rigid finished configuration to contain the product for shipping and storage, and also commonly includes a conventional paperboard structural layer. Product labeling and registration marks and the like may be printed on the paperboard layer or the outer thermoplastic layer. In the most preferred embodiment of the invention described below, the polyfoil web to be used comprises a laminate of, in order, a layer of low density polyethylene, paper stock, Surlyn.RTM., aluminum foil, Surlyn.RTM., and linear low density polyethylene. The low density polyethylene layer could also be a high density polyethylene, and the linear low density polyethylene layer could be a low density polyethylene.
The thermoplastic material forming the package interior must be capable of being sealed together to form hermetic seals. Typically, opposing thermoplastic layers are heated to a melting temperature so that they will fuse together. The thermoplastic and metallic foil layers act in concert to provide the hermetic barrier for the aseptic package. The metallic foil layer provides a light and oxygen barrier. The outer layer is commonly a thermoplastic material that can be heated so that the package seams and triangular tabs of excess material formed during final forming or bricking of the packages can be fused or tacked to the package sidewalls to form an aesthetically pleasing package.
Such polyfoil laminates may include spaced access means to enable the user to readily extract the product from the finished package.
Several methods and machines for forming aseptic and non aseptic packages or cartons from paper stock and laminated web materials are known. These methods and machines generally fall into two categories, blank fed and web fed.
In blank fed machines, the supply of web first is separately formed into cut and scored blanks. The blanks are then fed into the forming section of the machine one at a time and erected into containers. Many machines operate on several blanks at different stages of construction at a time. For aseptic packaging, the containers are sterilized, filled with a sterile product, and hermetically sealed close while in a sterile environment.
Some blank fed machines form the blanks into cartons intermittently, performing one assembly operation on the blank or carton at each station and advancing the blank or carton from station to station. Other blank fed machines operate semi-continuously by continuously advancing the blank to form the container and then intermittently advancing the container to sterilize, fill, and seal the container. One commercial intermittent type blank fed aseptic machine is Combiblok, Model No. CF 606A.
In web fed machines, the web is taken directly off the roll of web stock, scored (unless prescored on the roll) and fed into the machine. The machine then folds the web to form a column, seals the longitudinal edge to form a tube, fills the tube with a product, and clamps, seals, and severs the tube to form the packages. The web advance may be continuous, to gradually manipulate the web into sealed packages, or intermittent, to perform each assembly operation while the web is stationary or while the web is moving between stations.
For aseptic packaging, the web is sterilized and fed into a sterile machine section, so that the tube is sterile and the package is formed, filled and sealed in a sterile environment. One commercial automatic continuous feed aseptic machine is Tetra-Pak Model AB 9. Other known aseptic machines include International Paper Co.'s, web fed aseptic package machine, Model SA.
In many of the machines, reciprocating means are used to operate on the web either when the web or package is stationary, reciprocating into position and operation and then reciprocating out of position and operation when the web or package is advanced, or when the package advances, reciprocating with and operating on the package as it moves and then returning to the beginning of its stroke range while the web or package is stationary to operate on the following package.
The web fed machines may have one or more reciprocating means which reciprocate while the web continues to advance or opposing endlessly rotating means such as wheels or endless linked belts containing a plurality of identical means for sequentially operating on the web as the web advances at a substantially uniform speed. The present invention relates to an improvement in web fed type machines, and is designed to have a production rate substantially higher than that of presently known machines.
The primary problem with the aforementioned forming, filling, and sealing machines is that they are limited in the machine speed and web control required to make aseptic packages at a rate of speed higher than presently obtainable in an economically efficient manner. The production rate of known blank fed designs and machines are limited by the time required to erect a blank into a carton, fill the carton, and seal it. Intermittent and continuous web fed machines are limited by the rate at which the sealing mechanisms can clamp, seal, and sever the tube into packages or by the speed of the endlessly advancing linked chains or belts or rotating wheel on which the sealing mechanisms are mounted, or by the rate of reciprocating action of the sealing means to form each package.
Increasing the speed of continuous web fed machines can cause opposing wheels or belts to oscillate or bounce as the sealing mechanisms come in contact with each other to clamp and seal the package. This increases wear and decreases the useful life of the sealing mechanisms and could cause the wheels or belts to vibrate or become misaligned or untracked so that the sealing mechanisms would not seal accurately. Increasing machine speed is also limited by the dwell time required for clamping, heating, and cooling the web to form heremetic seals.
Similarly, increasing the frequency of reciprocation of the sealing means or other elements to increase the rate of production would also increase the wear and exaggerate any imbalance which could cause such an apparatus to shake itself apart. Adding a second reciprocating device sealing head to increase the rate has been applied with some success, see, for example, Model AB-9 manufactured by Tetra-Pak. However, this technique also suffers from having a limited maximum reciprocation and production rates and adds undue mechanical complexity to permit the plural means to reciprocate past each other without interference.
Adding a second or multiple production lines does not solve the problem of increasing the production rate of a single machine. Multiple production lines mounted on a single frame may achieve some efficiencies in sharing common elements, but it is effectively the same as two or multiple machines. The rate of production is not increased, only the volume. Such machines, e.g, the aforementioned Combiblok machine which has two parallel production lines, and other known models which have four production lines, are unduly bulky, mechanically complicated, and occupy a substantial amount of floor space. Further, the more common elements shared by the multiple lines, the more complicated and expensive the machine becomes, especially if the entire machine must be stopped to fix a problem present in only one of the lines.
A problem with using fixed wheels and opposed endless linked belts is that the structure required to maintain the sealing mechanisms spaced apart has no reliable means for altering the spacing between the sealing mechanisms to aid in preforming the package into a rectangular configuration. This typically requires the use of additional forming means. Further, for linked chains or belts, there are inherent timing and orientation problems in aligning the opposing sealing and severing means on opposite sides of the web given the mechanical flex inherent in moving linked chains or belts. The vibrations in the belts as they advance may result in misalignment, imperfect seals, and may cause the severing knife to contact and damage the opposing sealing head.
It is therefore an object of this invention to provide a form, fill, and seal machine with a single relatively slowly rotating structure having a plurality of sealing mechanisms for clamping, sealing, severing, and bricking a continuously advancing web of polyfoil material formed into a tube and filled with a fluent product into a plurality of packages.
It is another object of this invention to provide a volume control means to fix the volume of the tube as it is transversely clamped so that each package contains substantially the same quantity of product.
It is another object to adjust the orientation of the sealing mechanisms as they transversely clamp the tube to aid in controlling the volume of product in each package.
It is another object to selectively adjust the angular orientation of the sealing mechanisms on the structure so that adjacent sealing mechanisms move relative to one another to form the packages into about what will be their final bricked form.
It is a further object to maintain the web transversely clamped for a period of time sufficient to form hermetic seals, without over-stressing the mechanical limitations of the apparatus at high rates of production.